1. Technical Field
The present application relates generally to systems and methods for the detection of target analytes, the systems and methods including a nanotube aspect.
2. Discussion of Related Art
Chemical sensors and biosensors have been utilized for detecting many species, from contaminants in air (e.g., in air quality sensors) to the presence of particular DNA segments in blood samples or other samples. More recently, chemical and biosensors utilizing nanotubes, such as single-walled carbon nanotubes (SWNTs) have been proposed. See, e.g., J. Kong et al., Science, vol. 287, pp. 622-625 (Jan. 28, 2000), the entire contents of which are incorporated herein by reference.
Chemical sensors made of nanotubes may be functionalized or otherwise modified to become molecule-specific or species-specific sensors. Further details may be found in the following references, the entire contents of which are incorporated herein by reference: P. Qi et al., “Toward Large Arrays of Multiplex Functionalized Carbon Nanotube Sensors for Highly Sensitive and Selective Molecular Detection,” Nano Lett., vol. 3, no. 3, pp. 347-51 (2003); and Dai et al., “Carbon Nanotube Sensing,” U.S. Patent Publication No. 2002/0179434, filed on Jun. 18, 2002. On the other hand, such sensors may comprise non-functionalized semiconducting tubes and may sense for the presence of known chemicals, see, e.g., Kong, supra.
Optical nonlinearity of thin films of nanotubes has been described, e.g., by Rashid, et al., “Self-Assembled Organic Supramolecular Thin Films for Nonlinear Optics”, Organic Electronics 5 (2004) 147-155, the entire contents of which are incorporated herein by reference. Optical nonlinearity is a feature of some materials whereby the frequency of light reflected by a material is not equal to the frequency of the light that is transmitted onto that material. Lauret, J.-S., et al, “Third-order optical nonlinearities of carbon nanotubes in the femtosecond regime”, Applied Physics Letters vol. 85, no. 16 (2004) 3572-2574 have described. Optical nonlinearities generally arise in nanotubes due to a change in polarization in the molecular structure of the nanotubes from an applied field. Because of the quantum confinement of the π-electrons associated with their 1-D structure, nanotubes have a large and fast electronic third-order non-linearity. For further details see Margulis, VI A., et al “Non-degenerate optical four-wave mixing in single-walled carbon nanotubes”, Optics Communications, vol. 249 (2005) 339-349, the entire contents of which are incorporated herein by reference.